PPPLCommentaryGottfredson05
WHAT IF THE HEREDITARIAN HYPOTHESIS IS TRUE? Linda S. Gottfredson University of Delaware J. P. Rushton and A. R. Jensen (2005) review 10 bodies of evidence to support their argument that the long-standing, worldwide Black–White average differences in cognitive ability are more plausibly explained by their hereditarian (50% genetic causation) theory than by culture-only (0% genetic causation) theory. This com- mentary evaluates the relevance of their evidence, the overall strength of their case, the implications they draw for public policy, and the suggestion by some scholars that the nation is best served by telling benevolent lies about race and intelligence. Rushton and Jensen (2005) review the last 30 years of evidence on an important but spurned question: Is the average Black–White difference inphe- notypicintelligence partlygeneticin origin? Much relevant scientific evidence has accumulated since Jensen first asked the question in 1969, but openly addressing it still seems as politically unacceptable today as it was then. Taking the question seriously raises the possibility that the answer might be yes, which for some people is unthinkable. It is therefore no surprise that such research and researchers are often evaluated first against moral criteria and only secondarily, if at all, against scientific ones. My commentary therefore examines the Rushton–Jensen article against both the scientific and moral criteria typically applied to such work. The Hereditarian Hypothesis: What Is It? Rushton and Jensen’s (2005) hereditarian hypothesis is that Black–White differences in general intelligence (IQ, or the general mental ability factor,g) are “substantially” genetic in origin, which they quantify as 50% genetic and 50% environmental. They specify 50% genetic because they hypothesize that race differences are simply aggregated individual differences and because researchers commonly summarize within-group IQ heritability as 50%. Rushton and Jensen do not attempt to prove c…